1. Field of the Invention
The present invention relates to an electrical connector, and particularly to a straddle electrical connector having a two-stage connecting clamp attached to an edge of a circuit substrate such as a printed circuit board (PCB). The instant invention relates to a contemporarily filed application, Ser. No. 10/650,382 filed Aug. 27, 2003 with the same title and assignee with the instant application.
2. Description of Prior Art
So-called straddle electrical connectors are connected to edges of circuit boards, the circuit boards having electrical traces on both surfaces thereof. The straddle electrical connector has two rows of electrical contacts, each contact having a contact section. The edge of the circuit board is inserted between the rows of contact sections of the straddle connector. The contacts are connected to corresponding electrical traces using soldering techniques such as surface mount technology (SMT).
An example of a conventional straddle connector is shown in FIG. 6. The connector 8 is for being attached to an edge of a printed circuit board (PCB) 85. The connector 8 comprises an insulative housing 80, and a number of electrical contacts 81 arranged in two rows in the housing 80. Under normal conditions, contact sections 811 of the contacts 81 are inclined toward each other due to their resilience. The circuit board 85 comprises conductive pads 851, 852 on both surfaces of an edge, and solder coatings 853, 854 attached to the conductive pads 851, 852 respectively. A distance between soldering sections 812 of the contact sections 811 is less than an overall thickness of the circuit board 85 at the solder coatings 853, 854. Once the connector 8 is engaged on the edge of the circuit board 85, the contact sections 811 are soldered to corresponding conductive pads 851, 852 using an infra red light source or another kind of heat source.
When the connector 8 is mounted on the circuit board 85, the contact sections 811 are prone to scrape the solder coatings 853, 854 off from the conductive pads 851, 852. This is because the distance between the soldering sections 812 of the contact sections 811 is less than the overall thickness of the circuit board 85 at the solder coatings 853, 854. On the other hand, if the distance between the soldering sections 811 were greater than the overall thickness of the circuit board 85, it would be highly problematic or impossible to solder the soldering sections 811 to conductive pads 851, 852 via the solder coatings 853, 854. Yet when the solder coatings 853, 854 are scraped off, adequate soldering of the soldering sections 812 to the conductive pads 851, 852 cannot be obtained. Therefore, the reliability of the soldered connections may be substantially reduced.
A number of efforts has been made to improve the reliability of SMT techniques. For example, FIG. 7 shows a straddle connector 9 as disclosed in U.S. Pat. No. 5,584,708. The connector 9 comprises an insulative housing 91, electrical contacts 92 arranged in two rows in the housing 91, and a dielectric separator 93 movably located in a channel 923 of the housing 91. The housing 91 is molded from a suitable insulative plastic, and has a flat configuration for insertion of an edge of a circuit board 95 into the channel 923. Spaced conductive pads 951 are located on both surfaces of the circuit board 95 at the edge thereof. The conductive pads 951 are coated with solder (not shown). Connection sections 921 of the contacts 92 are brought to a position suitable for SMT connection. A distance between the opposite connection sections 921 of the contacts 92 is less than a thickness of the circuit board 95. Guide ends 9211 of the connection sections 921 are cooperatively flared for facilitating insertion of the circuit board 95.
Before the connector 9 is connected to the circuit board 95, the separator 93 is retained in the channel 923 near a mating face of the connector 9. The separator 93 keeps the connection sections 921 spaced apart so as not to touch the conductive pads 951 of the circuit board 95. When the circuit board 95 is inserted in the channel 923, a leading edge of the circuit board 95 comes into contact with the separator 93, and pushed the separator 93 further into the channel 923. When the circuit board 95 is completely inserted in the channel 923, the separator 93 is disposed in an inmost part of the channel 923. As a result, the connection sections 921 resiliently rebound and press onto the conductive pads 951. That is, when the connector 9 is connected to the edge of the circuit board 95, the distance between the connection sections 921 automatically changes to freely receive and then engage the circuit board 95. During this process, the connection sections 921 do not scrape solder from the conductive pads 951.
However, the connector 9 requires the flared guiding ends 9211 at distal ends of the contacts 92 in order to guide the circuit board 95 into the channel 923. Therefore, when the contacts 92 are soldered to the circuit board 95, the molten solder cannot completely cover the guiding ends 9211. As a result, when the connector 9 transmits high-frequency signals in operation, the guiding ends 9211 are prone to produce cross talk. The performance and specifications of the connector 9 are diminished.
A new straddle electrical connector that overcomes the above-mentioned disadvantages is desired.